Method and apparatus for reducing power fluctuations during preamble training in a multiple antenna communication system using cyclic delays

Abstract

Methods and apparatus are provided for reducing power fluctuations during preamble training in a multiple antenna communication system using cyclic delays. A preamble having a legacy portion and a high throughput portion is transmitted (or received) on each of N antennas, wherein at least a portion of the preamble on a first of the N antennas is delayed relative to at least the portion of the preamble on a second of the N antennas, wherein the delay is non-orthogonal amount to introduce variation across the preambles transmitted on the N transmit antennas. The legacy portion may be, for example, an 802.11 a/g preamble.

1. A method for transmitting data in a multiple antenna communication system having N transmit antennas, said method comprising the step of:
 transmitting a preamble having a legacy portion and a high throughput portion on each of said N transmit antennas, wherein a transmission of at least a portion of said preamble on a first of said N antennas is delayed relative to a transmission of said at least said portion of said preamble on a second of said N antennas, wherein said delay is a non-orthogonal amount to introduce variation across said preambles transmitted on said N transmit antennas. 
 
     
     
       2. The method of  claim 1 , wherein said legacy portion is an 802.11 a/g preamble. 
     
     
       3. The method of  claim 1 , wherein said preamble transmission on each of said N transmit antennas is delayed by approximately 5-10% of a symbol duration. 
     
     
       4. The method of  claim 1 , wherein said delay amounts are selected to maintain compatibility with one or more legacy devices. 
     
     
       5. The method of  claim 1 , wherein said preamble is one or more of a long preamble format or a short preamble format. 
     
     
       6. A multiple antenna communication system, comprising:
 N transmit antennas for transmitting a preamble having a legacy portion and a high throughput portion, wherein a transmission of at least a portion of said preamble on a first of said N antennas is delayed relative to a transmission of said at least said portion of said preamble on a second of said N antennas, wherein said delay is a non-orthogonal amount to introduce variation across said preambles transmitted on said N transmit antennas. 
 
     
     
       7. The multiple antenna communication system of  claim 6 , wherein said legacy portion is an 802.11 a/g preamble. 
     
     
       8. The multiple antenna communication system of  claim 6 , wherein said preamble transmission on each of said N transmit antennas is delayed by approximately 5-10% of a symbol duration. 
     
     
       9. The multiple antenna communication system of  claim 6 , wherein said delay amounts are selected to maintain compatibility with one or more legacy devices. 
     
     
       10. The multiple antenna communication system of  claim 6 , wherein said preamble is one or more of a long preamble format or a short preamble format. 
     
     
       11. A method for receiving data in a multiple antenna communication system having N antennas, said method comprising the step of:
 receiving a preamble having a legacy portion and a high throughput portion on each of said N transmit antennas, wherein a received portion of said preamble on a first of said N antennas is delayed relative to a received portion of said preamble on a second of said N antennas, wherein said delay is a non-orthogonal amount to introduce variation across said preambles transmitted on said N transmit antennas. 
 
     
     
       12. The method of  claim 11 , wherein said legacy portion is an 802.11 a/g preamble. 
     
     
       13. The method of  claim 11 , wherein said preamble reception on each of said N antennas is delayed by approximately 5-10% of a symbol duration. 
     
     
       14. The method of  claim 11 , wherein said delay amounts are selected to maintain compatibility with one or more legacy devices. 
     
     
       15. The method of  claim 11 , wherein said preamble is one or more of a long preamble format or a short preamble format. 
     
     
       16. A multiple antenna communication system, comprising:
 N receive antennas for receiving a preamble having a legacy portion and a high throughput portion, wherein a received portion of said preamble on a first of said N antennas is delayed relative to a received portion of said preamble on a second of said N antennas, wherein said delay is a non-orthogonal amount to introduce variation across said preambles transmitted on said N transmit antennas. 
 
     
     
       17. The multiple antenna communication system of  claim 16 , wherein said legacy portion is an 802.11 a/g preamble. 
     
     
       18. The multiple antenna communication system of  claim 16 , wherein said preamble reception on each of said N receive antennas is delayed by approximately 5-10% of a symbol duration. 
     
     
       19. The multiple antenna communication system of  claim 16 , wherein said delay amounts are selected to maintain compatibility with one or more legacy devices. 
     
     
       20. The multiple antenna communication system of  claim 16 , wherein said preamble is one or more of a long preamble format or a short preamble format.